/*-------------------------------------------------------------------------
 *
 * nbtcompare.c
 *      Comparison functions for btree access method.
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *      src/backend/access/nbtree/nbtcompare.c
 *
 * NOTES
 *
 *    These functions are stored in pg_amproc.  For each operator class
 *    defined on btrees, they compute
 *
 *                compare(a, b):
 *                        < 0 if a < b,
 *                        = 0 if a == b,
 *                        > 0 if a > b.
 *
 *    The result is always an int32 regardless of the input datatype.
 *
 *    Although any negative int32 (except INT_MIN) is acceptable for reporting
 *    "<", and any positive int32 is acceptable for reporting ">", routines
 *    that work on 32-bit or wider datatypes can't just return "a - b".
 *    That could overflow and give the wrong answer.  Also, one must not
 *    return INT_MIN to report "<", since some callers will negate the result.
 *
 *    NOTE: it is critical that the comparison function impose a total order
 *    on all non-NULL values of the data type, and that the datatype's
 *    boolean comparison operators (= < >= etc) yield results consistent
 *    with the comparison routine.  Otherwise bad behavior may ensue.
 *    (For example, the comparison operators must NOT punt when faced with
 *    NAN or other funny values; you must devise some collation sequence for
 *    all such values.)  If the datatype is not trivial, this is most
 *    reliably done by having the boolean operators invoke the same
 *    three-way comparison code that the btree function does.  Therefore,
 *    this file contains only btree support for "trivial" datatypes ---
 *    all others are in the /utils/adt/ files that implement their datatypes.
 *
 *    NOTE: these routines must not leak memory, since memory allocated
 *    during an index access won't be recovered till end of query.  This
 *    primarily affects comparison routines for toastable datatypes;
 *    they have to be careful to free any detoasted copy of an input datum.
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "utils/builtins.h"
#include "utils/sortsupport.h"


Datum
btboolcmp(PG_FUNCTION_ARGS)
{
    bool        a = PG_GETARG_BOOL(0);
    bool        b = PG_GETARG_BOOL(1);

    PG_RETURN_INT32((int32) a - (int32) b);
}

Datum
btint2cmp(PG_FUNCTION_ARGS)
{
    int16        a = PG_GETARG_INT16(0);
    int16        b = PG_GETARG_INT16(1);

    PG_RETURN_INT32((int32) a - (int32) b);
}

static int
btint2fastcmp(Datum x, Datum y, SortSupport ssup)
{
    int16        a = DatumGetInt16(x);
    int16        b = DatumGetInt16(y);

    return (int) a - (int) b;
}

Datum
btint2sortsupport(PG_FUNCTION_ARGS)
{
    SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);

    ssup->comparator = btint2fastcmp;
    PG_RETURN_VOID();
}

Datum
btint4cmp(PG_FUNCTION_ARGS)
{
    int32        a = PG_GETARG_INT32(0);
    int32        b = PG_GETARG_INT32(1);

    if (a > b)
        PG_RETURN_INT32(1);
    else if (a == b)
        PG_RETURN_INT32(0);
    else
        PG_RETURN_INT32(-1);
}

static int
btint4fastcmp(Datum x, Datum y, SortSupport ssup)
{
    int32        a = DatumGetInt32(x);
    int32        b = DatumGetInt32(y);

    if (a > b)
        return 1;
    else if (a == b)
        return 0;
    else
        return -1;
}

Datum
btint4sortsupport(PG_FUNCTION_ARGS)
{
    SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);

    ssup->comparator = btint4fastcmp;
    PG_RETURN_VOID();
}

Datum
btint8cmp(PG_FUNCTION_ARGS)
{
    int64        a = PG_GETARG_INT64(0);
    int64        b = PG_GETARG_INT64(1);

    if (a > b)
        PG_RETURN_INT32(1);
    else if (a == b)
        PG_RETURN_INT32(0);
    else
        PG_RETURN_INT32(-1);
}

static int
btint8fastcmp(Datum x, Datum y, SortSupport ssup)
{
    int64        a = DatumGetInt64(x);
    int64        b = DatumGetInt64(y);

    if (a > b)
        return 1;
    else if (a == b)
        return 0;
    else
        return -1;
}

Datum
btint8sortsupport(PG_FUNCTION_ARGS)
{
    SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);

    ssup->comparator = btint8fastcmp;
    PG_RETURN_VOID();
}

Datum
btint48cmp(PG_FUNCTION_ARGS)
{
    int32        a = PG_GETARG_INT32(0);
    int64        b = PG_GETARG_INT64(1);

    if (a > b)
        PG_RETURN_INT32(1);
    else if (a == b)
        PG_RETURN_INT32(0);
    else
        PG_RETURN_INT32(-1);
}

Datum
btint84cmp(PG_FUNCTION_ARGS)
{
    int64        a = PG_GETARG_INT64(0);
    int32        b = PG_GETARG_INT32(1);

    if (a > b)
        PG_RETURN_INT32(1);
    else if (a == b)
        PG_RETURN_INT32(0);
    else
        PG_RETURN_INT32(-1);
}

Datum
btint24cmp(PG_FUNCTION_ARGS)
{
    int16        a = PG_GETARG_INT16(0);
    int32        b = PG_GETARG_INT32(1);

    if (a > b)
        PG_RETURN_INT32(1);
    else if (a == b)
        PG_RETURN_INT32(0);
    else
        PG_RETURN_INT32(-1);
}

Datum
btint42cmp(PG_FUNCTION_ARGS)
{
    int32        a = PG_GETARG_INT32(0);
    int16        b = PG_GETARG_INT16(1);

    if (a > b)
        PG_RETURN_INT32(1);
    else if (a == b)
        PG_RETURN_INT32(0);
    else
        PG_RETURN_INT32(-1);
}

Datum
btint28cmp(PG_FUNCTION_ARGS)
{
    int16        a = PG_GETARG_INT16(0);
    int64        b = PG_GETARG_INT64(1);

    if (a > b)
        PG_RETURN_INT32(1);
    else if (a == b)
        PG_RETURN_INT32(0);
    else
        PG_RETURN_INT32(-1);
}

Datum
btint82cmp(PG_FUNCTION_ARGS)
{
    int64        a = PG_GETARG_INT64(0);
    int16        b = PG_GETARG_INT16(1);

    if (a > b)
        PG_RETURN_INT32(1);
    else if (a == b)
        PG_RETURN_INT32(0);
    else
        PG_RETURN_INT32(-1);
}

Datum
btoidcmp(PG_FUNCTION_ARGS)
{
    Oid            a = PG_GETARG_OID(0);
    Oid            b = PG_GETARG_OID(1);

    if (a > b)
        PG_RETURN_INT32(1);
    else if (a == b)
        PG_RETURN_INT32(0);
    else
        PG_RETURN_INT32(-1);
}

static int
btoidfastcmp(Datum x, Datum y, SortSupport ssup)
{
    Oid            a = DatumGetObjectId(x);
    Oid            b = DatumGetObjectId(y);

    if (a > b)
        return 1;
    else if (a == b)
        return 0;
    else
        return -1;
}

Datum
btoidsortsupport(PG_FUNCTION_ARGS)
{
    SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);

    ssup->comparator = btoidfastcmp;
    PG_RETURN_VOID();
}

Datum
btoidvectorcmp(PG_FUNCTION_ARGS)
{
    oidvector  *a = (oidvector *) PG_GETARG_POINTER(0);
    oidvector  *b = (oidvector *) PG_GETARG_POINTER(1);
    int            i;

    /* We arbitrarily choose to sort first by vector length */
    if (a->dim1 != b->dim1)
        PG_RETURN_INT32(a->dim1 - b->dim1);

    for (i = 0; i < a->dim1; i++)
    {
        if (a->values[i] != b->values[i])
        {
            if (a->values[i] > b->values[i])
                PG_RETURN_INT32(1);
            else
                PG_RETURN_INT32(-1);
        }
    }
    PG_RETURN_INT32(0);
}

Datum
btcharcmp(PG_FUNCTION_ARGS)
{
    char        a = PG_GETARG_CHAR(0);
    char        b = PG_GETARG_CHAR(1);

    /* Be careful to compare chars as unsigned */
    PG_RETURN_INT32((int32) ((uint8) a) - (int32) ((uint8) b));
}

Datum
btnamecmp(PG_FUNCTION_ARGS)
{
    Name        a = PG_GETARG_NAME(0);
    Name        b = PG_GETARG_NAME(1);

    PG_RETURN_INT32(strncmp(NameStr(*a), NameStr(*b), NAMEDATALEN));
}

static int
btnamefastcmp(Datum x, Datum y, SortSupport ssup)
{
    Name        a = DatumGetName(x);
    Name        b = DatumGetName(y);

    return strncmp(NameStr(*a), NameStr(*b), NAMEDATALEN);
}

Datum
btnamesortsupport(PG_FUNCTION_ARGS)
{
    SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);

    ssup->comparator = btnamefastcmp;
    PG_RETURN_VOID();
}
